From: Leigh Harrison (leigh.harrison@azzu.co.uk)
Date: Sat Aug 13 2005 - 18:01:44 GMT-3
Thanks for that fellas
All sorted and filtering like there's no tomorrow!
LH
-----Original Message-----
From: Jody Davis (joddavis) [mailto:joddavis@cisco.com]
Sent: 13 August 2005 20:53
To: Scott Morris; Leigh Harrison; ccielab@groupstudy.com
Subject: RE: Even/Odd route filtering
Scott,
You are correct! My bad..
The correct solution would look like:
Access-list 1 permit 192.168.0.0 0.0.254.0 (for evens) And Access-list 1
permit 192.168.1.0 0.0.254.0 (for odds)
Jody
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Scott Morris
Sent: Saturday, August 13, 2005 1:47 PM
To: Jody Davis (joddavis); 'Leigh Harrison'; ccielab@groupstudy.com
Subject: RE: Even/Odd route filtering
A '1' in the mask means that you don't care what the value is.
So looking at:
00000000 --> (starting value of the 3rd octet per 192.168.0.0)
00000001 --> mask you supplied
This only permits 0 or 1 in the 3rd octet.
You need a mask of 11111110 because the only one that MUST remain
unchanged is the 0 in the 1-bit position.
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jody Davis (joddavis)
Sent: Saturday, August 13, 2005 12:20 PM
To: Leigh Harrison; ccielab@groupstudy.com
Subject: RE: Even/Odd route filtering
As an example..
Filter only even routes from the 192.168.0.0..
Access-list 1 permit 192.168.0.0 0.0.1.0 (because the "3rd" octet of
address is "0" or an even, and the "1's" bit of the inverse mask is set
to "don't care", all evens will come through..
For odds,
Access-list 1 permit 192.168.1.0 0.0.1.0
Jody
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Leigh Harrison
Sent: Saturday, August 13, 2005 10:59 AM
To: ccielab@groupstudy.com
Subject: Even/Odd route filtering
All,
If I have the subnet 10.1.n.n - 10.50.n.n and I wanted to filter even
routes out of one interface and odd routes out of a different one, how
would I achieve this?
I know that all I would need to do is match on the 16th bit and ensure
that it is a "1" or a "0" in order to make it odd or even. I know that
I could write a big list, but I would like to match on the one bit. Is
this even possible ?!
Many thanks in advance,
LH
Leigh Harrison
Technical Consultant
Azzurri Communications
Castleton Mill,
Castleton Close,
Leeds,
LS12 2DS
Email: Leigh.Harrison@azzu.co.uk <mailto:Leigh.Harrison@azzu.co.uk>
Mobile: 07989 605 806
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Web: www.azzu.co.uk <http://www.azzu.co.uk/>
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